This invention relates to human powered vehicles in general, and to automatic transmissions therefor, in particular.
Human powered cycles, such as bicycles, and some tricycles, often have a variable speed transmission. With known bicycles, such as shown in FIG. 1, there are various types of variable transmission. Internal rear hub transmissions, typically 3 speed, are known. With such transmissions, the rider rotates pedals 10 that are connected to a chain ring 12 through a crank 11, which, in turn, through a chain 14, is connected to a rear wheel sprocket 16. The sprocket is connected through a variable internal hub transmission (not shown) to the wheel 18. (FIG. 1 is a composite, showing aspects of various, different types of prior art transmissions. It does not show the internal hub transmission or a cable thereto, but, rather, shows a type of rear wheel transmission that is described below. Since the internal hub type transmission is well known, and not germane to the invention, it is not shown specifically. FIG. 1 is used herein only to show where such known, internal hub transmissions reside.) The internal workings of the hub change according to controls manually manipulated by the user, such as through a handlebar-mounted lever that connects to the hub through a cable.
Another popular type of known transmission, such as shown with reference to FIG. 1, employs a multi-sprocket rear cartridge 18, for instance mounted on the rear hub 16, having several, typically between three and eight variable diameter sprockets 20. A rear derailleur 22 engages the chain 14, as described above, and, again under manual control of the operator, typically through a cable 24, moves the chain from engagement with one of the sprockets to another. By changing the active sprocket to one with a different diameter, the gear ratio of the operable transmission elements is changed. A larger rear sprocket 20 reduces the effort required to rotate the rear wheel 26 against a load, and is typically referred to as a xe2x80x9clower gear.xe2x80x9d A smaller rear sprocket 20 increases the effort required to rotate the rear wheel against a load, but also increases the circumferential distance covered by the rear wheel for a single rotation of the pedals 10, and is referred to as a xe2x80x9chigher gear.xe2x80x9d Typically, the cable moves the derailleur such that it directs the chain from a higher to a lower gear while a spring within the derailleur returns the chain from a lower to a higher gear when the user relaxes the tension on the cable by moving a lever.
A similar type of transmission also employs a set of sprockets having different diameters, but, rather than being mounted on the rear hub, such varying diameter sprockets 28 are coupled directly to the pedal assembly, so that one rotation of the pedals causes one full rotation of the front sprockets 28. The sprockets are typically referred to as chain ring sets. A front derailleur 30 engages the chain 14, and, again under manual control of the operator, typically through a cable (not shown), moves the chain 14 from engagement with one of the chain rings 32 to another 34. By changing the active chain ring to one with a different diameter, the gear ratio of the operable transmission elements is changed. A larger 32 front chain ring 28 increases the effort required to rotate the rear wheel 26 against a load, and is typically referred to as a xe2x80x9chigher gear.xe2x80x9d A smaller 34 front chain ring 28 decreases the effort required to rotate the rear wheel against a load, but also decreases the circumferential distance covered by the rear wheel for a single rotation of the pedals 14, and is referred to as a xe2x80x9clower gear.xe2x80x9d Typically, the cable moves the derailleur such that it directs the chain from a lower to a higher gear while a spring within the derailleur returns the chain from a higher to a lower gear when the user relaxes the tension on the cable by moving a lever.
Thus, a higher gear is obtained by engaging a smaller rear sprocket 18 or a larger front chain ring 28. A lower gear is obtained by engaging a larger rear sprocket or a smaller front chain ring.
Often, bicycles use both a front and rear derailleur type transmission, thereby obtaining a large number of effective gear ratios, equal to the product of the number of rear sprockets 18 times the number of front chain rings 28. However, often, some of the gear ratio combinations are very nearly equal to others of the combinations, and often the extreme combinations, such as the largest rear sprocket and the largest front chain ring (which would result in an intermediate gear ratio) are not comfortably obtained without the chain rubbing excessively on the chain ring and sprocket. Thus, a nominally eighteen speed transmission (six rear sprockets and three front chain rings) might have only eight to ten significantly different gear ratios.
There are other types of transmissions also, which are known to the art.
All of the above mentioned transmissions are typically available in a manual embodiment, in which the user decides when to change gears (xe2x80x9cshift gearsxe2x80x9d) and does so by manually moving some element of the transmission system. Typically, the movable element is a lever near the front of the bicycle. Over the years, many different types of levers have been used. (For purposes of illustration, only, several types are shown in FIG. 1. Only one type would be present for any actual bicycle.) A popular three speed-internal hub transmission used a single handle mounted lever (not shown). Other cartridge and chain ring models use levers 40 mounted on the handle bars, or 42 on the down tube and 44 at the ends of the handle bar tubes (both lever and rotary types). A relatively recent configuration incorporates the gear shift levers into handles 46 that are also part of the braking assembly. With some models, a unitary lever actuates both a brake and a gear shift, while in others, tandem, nested levers are used, one for braking and one for shifting. Some shifting lever mechanisms use one lever for shifting from a lower gear to a higher gear, and another for the reverse direction.
A problem with all of the conventional transmissions that use a rear cartridge 18 or/and a front set of chain rings 28, is that shifting the chain from one toothed gear wheel to another, when shifting from a higher to a lower gear, such as when climbing a hill, typically occurs at a time when the user wants to be applying power to the transmission. However, if power is applied at the wrong moment, as the chain is intermediate between one ring and another, the next chain ring does not pick up the chain, and the shifting mechanism malfunctions. The result is grinding and wear of all of the components, as well as loss of power and momentum, which often necessitates shifting to an even lower gear. There are some semi-automated shifting mechanisms which delay the actual shifting until the components are aligned properly to avoid missing.
One reason that gear missing occurs is that the chain is being moved adjacent the gear wheels, right at the circumferential location around the gear wheel where the chain engages the gear wheel, and where power is transmitted from the gear wheel to the chain (front gear wheels), or vice versa (rear gear wheels). In other words, the chain is removed from the first gear wheel within the driving zone, and is deposited onto the next gear wheel within the driving zone. As shown in FIG. 1, the xe2x80x9cdriving zonexe2x80x9d is roughly the forward half of the chain ring (for a front chain ring), indicated between the arrows Dz. (For a rear chain ring sprocket, the driving zone is roughly the rearward half.)
Force is generated between the chain and the chain ring in part due to the torque applied by the user pushing on the pedals, and in part by the tension in the chain, which is established by a spring in the rear derailleur 22. Thus, as the chain is moving over toward the chain ring, torque is being applied by the pedals to the chain ring. If there is no engagement between the chain and the chain ring, then no load resists the torque and the chain wheel just spins. Or more commonly, if the engagement is positive, but less than some a minimum degree, the chain is not retained by the chain wheel, and the chain wheel spins while the teeth grind against the chain links, thereby eventually damaging both, as well as failing to apply power to the task of moving the cycle.
Another drawback with conventional systems is that the user must decide when to shift. Many users are not skilled at making such decisions, and make the decision at the wrong time. Further, the user must manually make the move. This requires, in most cases, removing the hand from the normal driving position, and moving it to a shifting mechanism. In the case of down tube, and centrally mounted handle bar shifters, the shifting hand can no longer control the handlebars. This is the reason for the popularity of bar end and brake mechanism shifters. However, bar end shifters are often very stiff, and awkward to actuate. Brake mechanism shifters are very expensive, fragile, and mechanically complicated.
Automatic shifting transmissions have been proposed with many different forms of mechanisms, attempting to solve the foregoing problems. None have been commercially successful, and the reasons are too many and various to explore here. Many have mechanisms that actuate in the driving zone and must move against the resistance of a driving band (typically a chain) as power is applied to it by the user. Many have complicated or delicate mechanisms that cannot withstand the harsh environment cycles, particularly bicycles, encounter. Many cannot be adequately governed, or require large forces to shift the gears.
Another drawback of many of the known automatic shifting mechanisms, is that they can not be retrofitted onto the millions of existing bicycles. In fact, some designs cannot even be used on a conventional bicycle frame, but require special configurations of the supports and stays.
Thus, the several objects of the present invention include to provide a shifting mechanism for a human powered wheeled cycle, particularly a bicycle, which is not prone to slipping when shifting. Another object is to provide a shifting mechanism that can be simply and reliably automated, so that the user need not decide when to shift, or displace his/her hands from the driving position to make the shift. Another object of the invention is to provide a shifting mechanism that can be automated, which can be retrofitted onto existing bicycles, and that can be incorporated into new bicycles with standard frames. Another object of the invention is to provide a transmission with the foregoing properties, which is economical to manufacture and maintain.
In general, according to the present invention, a shifting mechanism for a cycle, such as a bicycle, is provided that has at least two gear wheels, of which at least one is segmented. The segments are movable into and out of a driving position. Motion of the segments occurs at a circumferential location out of the driving zone, at a location where the driving band, typically a chain, is not contacting the segment. The shifting mechanism can be provided at the front chain ring, or at the rear, gear sprocket. For a front chain wheel, the free zone is generally the rearward half of the chain ring, while for the rear gear sprocket, the free zone is generally the forward half. The moving segments can be toothed gates which flip perpendicularly to the plane in which the chain resides. The gates may be actuated by a moving mechanism powered by an actuator, such as a D.C. motor, under control of a signal processor, typically a microprocessor. The signal processor also takes as an input a speed signal based on the rotational speed of the cycle wheels, or the cadence of the pedal or a combination thereof.
A preferred embodiment of the invention is a transmission for a bicycle, the transmission comprising a variable configuration gear wheel, having components that move relative to each other from a first position to a second position, where, in the second position, the movable components engage a bicycle chain in a driving position. The movable components are configured and arranged so that the relative motion takes place only in a free zone where the chain and movable components are free of each other. The movable components are arranged such that when any movable component engages the chain, the movable component is stationary relative to all except, at most, one other of the movable components. The variable configuration gear wheel may be a front chain wheel, in which case the free zone is a zone behind the chain wheel, generally between it and a rear wheel of the bicycle. Alternatively, the variable configuration gear wheel may be a rear sprocket wheel, in which case the free zone is a zone ahead of the sprocket wheel, generally between it and a chain wheel of the bicycle.
The movable component is movable to the second position along a path having a component that is perpendicular to a plane in which the chain lies. The transmission also includes a mover mechanism to move each of the movable components to the second position. Either the same, or another mover mechanism moves each of the movable components from the second to the first position.
Another preferred embodiment of the invention is a transmission component for a cycle having a driving crank and a driven wheel, torque being transmitted from the driving crank through a bracket, that is coupled thereto, to the wheel by an endless power band that engages the transmission component at a driving zone and that is free from the transmission component at a free zone. The transmission component is coupled to the bracket and comprises a variable configuration ring assembly that comprises: a support and, coupled to the support, a plurality of ring components. Each ring component is movable from a driving position to a non-driving position. Each of the ring components comprises at least one band engaging elements around a perimeter. The ring components are arranged such that, if the ring component is in the driving position, then the band engaging elements: form an outermost, segmented band ring; are driven circumferentially if the crank is moved in a driving direction; lie in a driving plane; and engage the band in the driving zone but are free from the band in the free zone. The ring components are also arranged such that, if the ring component is not in the driving position, then the band engaging elements lie out of the driving plane and are free from the band in both the driving zone and in the free zone.
Typically, each ring component has a couple to the support that constrains relative motion of the ring component such that motion of the ring component from the non-driving position to the driving position has a vector component that is perpendicular to the driving plane.
A version of this embodiment of the invention further has a ring component mover, arranged and operative to move at least one of the ring components from the non driving position to the driving position only when the ring component is in the free zone. There may be a single mover for each ring component, one for all, or more than one mover may handle some but not all of the ring components.
A typical embodiment of the invention further comprises a radially innermost band ring, having a plurality of band engaging elements around a perimeter. The innermost band ring is coupled by the bracket to the driving crank such that the band engaging elements: are driven circumferentially if the crank is driven circumferentially; lie in the driving plane; and engage the band in the driving zone and are free from the band in the free zone, if the innermost band ring engages the band.
In a very useful embodiment of the invention, the cycle is a bicycle, and the wheel comprises a rear wheel of the bicycle. Typically, the endless band comprising a roller chain, the band engaging elements being sized and shaped to engage links of the chain. Alternatively, the endless band may be a posi-drive type belt, the band engaging elements being sized and shaped to engage the posi-drive type belt.
In many embodiments, the ring components are arranged such that when engagement with the band commences, the ring component is fully in the driving position and is not moving from the non-driving position to the driving position.
According to another embodiment of the invention, the outermost plurality of ring components are designated xe2x80x9cgates.xe2x80x9d The invention further comprises, a gate mover, operative to move at least one of the gates, only where the at least one gate is in the free zone: from the non-driving position to the driving position; and from the driving position to the non-driving position. As mentioned above, there may be one gate mover for all of the outermost gates, or one for each, or more than one, each of which handles some, but not all, of the gates.
The innermost band ring is arranged relative to the outer band ring such that if the innermost band ring engages a band, and the ring components of the outer band ring are sequentially moved from the non-driving position to the driving position, then the band transfers from the innermost band ring to the outer band ring by engagement with the moved ring components. Conversely, if the outer band ring engages a band, and the ring components of the outer band ring are sequentially moved from the driving position to the non-driving position, then the band transfers from the outer band ring to the innermost band ring.
In a preferred embodiment, a hinge couples each gate to the support.
The plurality of gates are typically located such that the segmented outermost band ring circumscribes the innermost band ring if the outermost gates are in the driving position.
According to an embodiment of the invention that provides more speed possibilities, the transmission further comprises a radially intermediate segmented band ring, carried by the support, so that it is also driven circumferentially if the crank is driven circumferentially. The intermediate band ring comprises a plurality of intermediate movable gates, each of the plurality of intermediate gates carrying at least one band engaging elements along a peripheral region. Each of the plurality of intermediate gates are movable from a non-driving position with the band engaging elements out of the driving plane, to a driving position with the band engaging elements in the driving plane, such that the intermediate band engaging elements engage the band in the driving zone and are free from the band in the free zone if the intermediate band ring engages the band. For the plurality of intermediate gates, there is at least one gate mover, operative to move each the intermediate gate, only where the gate is in the free zone. The gate mover is operative to move the gates from the non-driving position to the driving position and from the driving position to the non-driving position. The plurality of intermediate gates are located such that the intermediate segmented band ring circumscribes the innermost band ring, and is circumscribed by the outermost segmented band ring if the intermediate and outermost movable gates are in the driving position.
In a typical preferred embodiment, the gate mover is movable. Each of the gates comprises a gate placer, arranged to be contacted by the gate mover. The gate placer may comprise an angled ramp, carried by the gate. Each of the gates also typically comprises a gate picker, which may also be an angled ramp carried by the gate, arranged to be contacted by the gate mover. The gate mover may have a placer trigger that is movable to contact the gate placer of a gate when the gate is in the free zone and a picker trigger that is movable to contact the gate picker when the gate is in the free zone.
In still another preferred embodiment, the gate mover is movable at selectable times to a placing position in which it contacts the gate as the gate passes by the gate mover, thereby causing the gate to move from the non-driving position to the driving position. The gate mover may be movable to the placing position by a cable linkage. More typically, the gate mover is movable to the placing position at selectable times based on a rotational velocity of the driven wheel. In such a case, the invention further comprises a sensor which, upon activation, generates a signal that corresponds to rotational velocity of the driven wheel. Coupled to the sensor is an outer ring actuator, actionable to move the gate mover to the placing position at times that the rotational velocity of the driven wheel increases to an outermost upshift velocity.
In a specifically preferred embodiment of the invention, the gate mover is further movable at selectable times to a picking position in which it contacts the gate as the gate passes by the gate mover, thereby causing the gate to move from the driving position to the non-driving position. The gate mover is also movable to the picking position at selectable times based on a rotational speed of the driven wheel. Typically, the outermost actuator is further actionable to move the gate mover to the picking position at times that the rotational velocity of the driven wheel decreases to an outermost downshift velocity. It is helpful if the outermost downshift velocity is less than the outermost upshift velocity.
In an embodiment, as described above, having an outermost, innermost, and intermediate band rings, the intermediate gate mover is also typically movable, for both picking and placing, by an intermediate gate actuator at times based on wheel velocity, with upshift and downshift velocities that are coordinated with the upshift and downshift velocities for the outermost band ring. The intermediate upshift velocity is less than the outermost upshift velocity.
According to another beneficial aspect of the invention, there is a controller that controls actuation of the outer ring actuator. The controller may be a microprocessor. The ring actuator may be a D.C. motor, a servo motor, or a solenoid. A particularly useful type of D.C. motor is a small, 1.5 volt motor having copper wipers.
A preferred aspect of the invention is a transmission for a cycle, according to any of the embodiments described above, either as a retrofit or as an original equipment feature. Also an aspect of the invention is an entire bicycle, or other type cycle, employing any of the embodiments of the transmission of the invention described above.